The present invention relates to a semiconductor device. More particularly, the present invention relates to a semiconductor device including a recess transistor and a method of fabricating the same.
As a semiconductor device becomes smaller and more highly integrated, a technology for reducing the size of a semiconductor device has been required. Due to the trends in miniaturization and integration of semiconductor devices, the design rule for the semiconductor device is reduced so that a channel length of a metal oxide semiconductor field effect transistor (MOSFET) is decreased.
Since the reduced channel length decreases a distance between a source region and a drain region, there is a difficulty in controlling a short channel effect (SCE), e.g., a voltage of the drain region affects voltages of the source region and the channel region. As a result, active switch elements are degraded. The narrow gap between the source region and the drain region causes a punch-through phenomenon between a source region and a drain region. In order to prevent the punch-through phenomenon, the gate can be formed by recessing the semiconductor substrate and filling it with a gate electrode, thereby increasing an effective channel length. This structure is called a recess field effect transistor (FET) structure. The recess FET structure reduces the punch-through phenomenon by increasing the effective channel length.
However, the recess FET structure is weak in controlling degradation of a threshold voltage Vt, thereby lowering a threshold voltage and generating a leakage current when the transistor is in an OFF state. Since the semiconductor substrate is etched at a relatively deep level to form the recess FET structure, the device characteristic such as a leakage current characteristic in the transistor OFF state is degraded by the passing gate effect as well as the neighboring gate effect.